[PATCH 2/2] xfs: always scrub record/key order of interior records

Darrick J. Wong
2022-12-30T22:41:50Z

In commit d47fef9342d0, we removed the firstrec and firstkey fields of
struct xchk_btree because Christoph thought they were unnecessary
because we could use the record index in the btree cursor. This is
incorrect because bc_ptrs (now bc_levels[].ptr) tracks the cursor
position within a specific btree block, not within the entire level.

The end result is that scrub no longer detects situations where the
rightmost record of a block is identical to the leftmost record of that
block's right sibling. Fix this regression by reintroducing record
validity booleans so that order checking skips *only* the leftmost
record/key in each level.

Fixes: d47fef9342d0 ("xfs: don't track firstrec/firstkey separately in xchk_btree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/scrub/btree.c | 14 ++++++++------
fs/xfs/scrub/btree.h | 8 +++++++-
2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
index 615f52e56f4e..2dfa3e1d5841 100644
--- a/fs/xfs/scrub/btree.c
+++ b/fs/xfs/scrub/btree.c
@@ -151,11 +151,12 @@ xchk_btree_rec(

trace_xchk_btree_rec(bs->sc, cur, 0);

- /* If this isn't the first record, are they in order? */
- if (cur->bc_levels[0].ptr > 1 &&
+ /* Are all records across all record blocks in order? */
+ if (bs->lastrec_valid &&
!cur->bc_ops->recs_inorder(cur, &bs->lastrec, rec))
xchk_btree_set_corrupt(bs->sc, cur, 0);
memcpy(&bs->lastrec, rec, cur->bc_ops->rec_len);
+ bs->lastrec_valid = true;

if (cur->bc_nlevels == 1)
return;
@@ -198,11 +199,12 @@ xchk_btree_key(

trace_xchk_btree_key(bs->sc, cur, level);

- /* If this isn't the first key, are they in order? */
- if (cur->bc_levels[level].ptr > 1 &&
- !cur->bc_ops->keys_inorder(cur, &bs->lastkey[level - 1], key))
+ /* Are all low keys across all node blocks in order? */
+ if (bs->lastkey[level - 1].valid &&
+ !cur->bc_ops->keys_inorder(cur, &bs->lastkey[level - 1].key, key))
xchk_btree_set_corrupt(bs->sc, cur, level);
- memcpy(&bs->lastkey[level - 1], key, cur->bc_ops->key_len);
+ memcpy(&bs->lastkey[level - 1].key, key, cur->bc_ops->key_len);
+ bs->lastkey[level - 1].valid = true;

if (level + 1 >= cur->bc_nlevels)
return;
diff --git a/fs/xfs/scrub/btree.h b/fs/xfs/scrub/btree.h
index 26c499925b5e..def8da9c4b4a 100644
--- a/fs/xfs/scrub/btree.h
+++ b/fs/xfs/scrub/btree.h
@@ -31,6 +31,11 @@ typedef int (*xchk_btree_rec_fn)(
struct xchk_btree *bs,
const union xfs_btree_rec *rec);

+struct xchk_btree_key {
+ union xfs_btree_key key;
+ bool valid;
+};
+
struct xchk_btree {
/* caller-provided scrub state */
struct xfs_scrub *sc;
@@ -40,11 +45,12 @@ struct xchk_btree {
void *private;

/* internal scrub state */
+ bool lastrec_valid;
union xfs_btree_rec lastrec;
struct list_head to_check;

/* this element must come last! */
- union xfs_btree_key lastkey[];
+ struct xchk_btree_key lastkey[];
};

/*